The entente between the UK and France was struggling to remain cordiale on Friday as the boss of Britain’s favourite retailer was forced into an embarrassing apology hours after launching an attack on France, labelling it “sclerotic, hopeless and downbeat”.

Andy Street, managing director of John Lewis, described France as a “finished” country where “nothing works and, worse, nobody cares about it”.

But as his comments swept across Twitter and anger mounted in France – where John Lewis has plans to boost its business with a new French language website – Street was forced into an abject “Je m’excuse”.

The department store boss said he regretted his comments, which were “supposed to be tongue in cheek” and “lighthearted views”. He added: “On reflection I clearly went too far and apologise unreservedly.

Street’s tirade came at a John Lewis awards event after a business trip to Paris, with a return journey to London on a delayed Eurostar train from Paris Gare du Nord, which he called “the squalor pit of Europe”. He also advised investors with money in French firms to get their cash out as quickly as possible.

Street even included an attack on a retail award he was handed at the Paris business conference. The trophy, he said, was “made of plastic and is frankly revolting”. He added: “If I needed any further evidence of a country in decline, here it is. Every time [I see the award] I shall think, ‘God help France’”.

Street wasn’t even impressed by French food and wine, which he said was much better in London.

His speech – and sense of humour – at one point risked sparking a minor international incident as his attack came on the eve of a visit to Britain by the new French prime minister Manuel Valls.

Jean-Louis Missika, deputy mayor of Paris, described Street’s statements as “false and idiotic”, but he had some sympathy with his view of the Gare du Nord. Its problems were “known and being addressed”, he said. “We are able to identify our problems, you know, and do something to treat them.”

But Guillaume Maujean, the editor of French financial daily Les Échos, said the 50-year-old John Lewis chief’s comments were “grotesque” French-bashing.

The Franco-British Council said Street’s attack was an example of “a festering antagonism with the French and France from the British”.

The French embassy in London said: “France is the fifth biggest economy in the world, the second in Europe … so obviously many foreign businesses do not seem to share Mr Street’s view.

“Everyone who has lived in France knows that it enjoys world-class public services. Public transport, for example, is excellent, and at a price that Mr Street is unlikely to find in many countries.”

Valls has his first meeting with David Cameron in London on Monday. No 10 declined to take a view on the bagarre, but pointed out that the UK values its strong cross-Channel relationship.

The French embassy urged Street to attend Valls’ speech to the Lord Mayor of the City of London and business leaders at the Guildhall on Monday. “If Mr Street takes time to listen he will be in no doubt that France is not sclerotic, and is implementing wide-ranging reforms including cutting taxes for businesses.”

Valls, however, might actually agree with some of Street’s sentiments. He recently described the French economy as “foutu”, which can be translated variously as “knackered”.

While Street apologised, Tory MP Michael Fabricant, a long-standing friend of Street, took to Twitter to pour some cognac on the fire.

“Anyone travelling on the filthy, graffiti-covered Paris Metro will agree with the boss of John Lewis,” he said in a now-deleted tweet. Another Fabricant tweet read: “French embassy getting their pantaloons in a twist. France is in recession and over 360,000 French working in UK because of mass unemployment.” .

Fabricant also pointed out that France’s finance minister Emmanuel Macron had his own doubts about the health of the nation. Macron said last month: “France is sick. It’s not well. We have to describe the situation as it is.”

Street also found a sympathetic ear in Simon Walker, director general of the Institute of Directors, which represents British company bosses.

“I’m a little surprised. I have a house in France and spend as much time as I can in France … the wine is better, the people are stylish … I even quite like Gard du Nord,” he said.

But he added: “The French economy is a disaster area and I think his analysis is basically right. I have certainly worked in companies that wouldn’t invest in France because of its rigid and inflexible labour market…

“France is protectionist and protectionism is something that has to be fought. Sclerotic is a legitimate word to use with regard to France and other parts of the eurozone as well.

“I think you invest where you can find open markets and that’s always a bit of a myth with France, because this is the country that blocked the takeover of a yoghurt company,” Walker said, referring to the fact that 10 years ago the French government declared that Danone, famous for its Activia yoghurt and Evian water, was a national champion which could never been taken over by a foreign company.

The French economy has been hampered by low growth and poor tax receipts in recent years. David Cameron annoyed the French government two years ago when he promised to “roll out the red carpet” for French companies seeking to avoid higher taxes on the rich.

Street is not the first businessman to insult France. Last year Maurice Taylor, boss of US tyre company Titan International, did not take kindly to an offer to buy a down-at-heel tyre factory in France. “How stupid do you think we are?” he said.